1. Field of the Invention
The invention relates to improvements in fibre optic gyroscopes. Such devices, otherwise known as a fibre resonator gyros, comprise a fibre or fibres defining a resonator loop through which clockwise (CW) and counter-clockwise (CCW) components of radiation are passed. Both CW and CCW directions are maintained at resonance by a suitable control and the difference in frequency between the resonances is a measure of the rate of rotation applied to the gyro.
2. Discussion of Prior Art
Ideally such devices will have high sensitivity to changes in rotation rate, low backscatter and minimal Kerr effect. However, in practice it has proved difficult or even impossible to satisfy all these criteria simultaneously. For example, a fibre optic gyroscope of the ring resonator type which is characterised by having a relatively short loop of between, say, 10 and 30 meters and in which the light from a narrow band source passes around the loop a relatively large number of times, has the disadvantage of significant backscatter throughout the light path, although the sensitivity is relatively high. Furthermore, a fibre optic gyroscope of the reciprocal interferometer type which is characterised by having a relatively long loop of between, say, 300 and 1000 meters and in which the light from a broad band source passes around the loop a relatively small number of times, has the disadvantage of relatively low sensitivity, but does not suffer significantly from backscatter or the Kerr effect.